170 research outputs found
Testing Bell's inequality with two-level atoms via population spectroscopy
We propose a feasible experimental scheme, employing methods of population
spectroscopy with two-level atoms, for a test of Bell's inequality for massive
particles. The correlation function measured in this scheme is the joint atomic
function. An inequality imposed by local realism is violated by any
entangled state of a pair of atoms.Comment: 4 pages, REVTeX, no figures. More info on
http://www.ligo.caltech.edu/~cbrif/science.htm
Constructive updating/downdating of oblique projectors: a generalization of the Gram-Schmidt process
A generalization of the Gram-Schmidt procedure is achieved by providing
equations for updating and downdating oblique projectors. The work is motivated
by the problem of adaptive signal representation outside the orthogonal basis
setting. The proposed techniques are shown to be relevant to the problem of
discriminating signals produced by different phenomena when the order of the
signal model needs to be adjusted.Comment: As it will appear in Journal of Physics A: Mathematical and
Theoretical (2007
Nonlocality, Bell's Ansatz and Probability
Quantum Mechanics lacks an intuitive interpretation, which is the cause of a
generally formalistic approach to its use. This in turn has led to a certain
insensitivity to the actual meaning of many words used in its description and
interpretation. Herein, we analyze carefully the possible mathematical meanings
of those terms used in analysis of EPR's contention, that Quantum Mechanics is
incomplete, as well as Bell's work descendant therefrom. As a result, many
inconsistencies and errors in contemporary discussions of nonlocality, as well
as in Bell's Ansatz with respect to the laws of probability, are identified.
Evading these errors precludes serious conflicts between Quantum Mechanics and
both Special Relativity and Philosophy.Comment: 8&1/2 pages revtex; v2: many corrections, clairifications &
extentions, all small; v3: editorial scru
Is "entanglement" always entangled?
Entanglement, including ``quantum entanglement,'' is a consequence of
correlation between objects. When the objects are subunits of pairs which in
turn are members of an ensemble described by a wave function, a correlation
among the subunits induces the mysterious properties of ``cat-states.''
However, correlation between subsystems can be present from purely non-quantum
sources, thereby entailing no unfathomable behavior. Such entanglement arises
whenever the so-called ``qubit space'' is not afflicted with Heisenberg
Uncertainty. It turns out that all optical experimental realizations of EPR's
\emph{Gedanken} experiment in fact do not suffer Heisenberg Uncertainty.
Examples will be analyzed and non-quantum models for some of these described.
The consequences for experiments that were to test EPR's contention in the form
of Bell's Theorem are drawn: \emph{valid tests of EPR's hypothesis have yet to
be done.}Comment: 5 p. LaTeX + 3 eps & 1 ps fig; v2:typos fixe
Propagation of local decohering action in distributed quantum systems
We study propagation of the decohering influence caused by a local
measurement performed on a distributed quantum system. As an example, the gas
of bosons forming a Bose-Einstein condensate is considered. We demonstrate that
the local decohering perturbation exerted on the measured region propagates
over the system in the form of a decoherence wave, whose dynamics is governed
by elementary excitations of the system. We argue that the post-measurement
evolution of the system (determined by elementary excitations) is of importance
for transfer of decoherence, while the initial collapse of the wave function
has negligible impact on the regions which are not directly affected by the
measurement.Comment: 6 REVTeX pages, no figures. Introduction and discussion sections are
extende
Bell inequalities for entangled kaons and their unitary time evolution
We investigate Bell inequalities for neutral kaon systems from Phi resonance
decay to test local realism versus quantum mechanics. We emphasize the unitary
time evolution of the states, that means we also include all decay product
states, in contrast to other authors. Only this guarantees the use of the
complete Hilbert space. We develop a general formalism for Bell inequalities
including both arbitrary "quasi spin" states and different times; finally we
analyze Wigner-type inequalities. They contain an additional term, a correction
function h, as compared to the spin 1/2 or photon case, which changes
considerably the possibility of quantum mechanics to violate the Bell
inequality. Examples for special "quasi spin" states are given, especially
those which are sensitive to the CP parameters epsilon and epsilon'.Comment: REVTeX, 22 page
Entanglement, Bell Inequalities and Decoherence in Particle Physics
We demonstrate the relevance of entanglement, Bell inequalities and
decoherence in particle physics. In particular, we study in detail the features
of the ``strange'' system as an example of entangled
meson--antimeson systems. The analogies and differences to entangled spin--1/2
or photon systems are worked, the effects of a unitary time evolution of the
meson system is demonstrated explicitly. After an introduction we present
several types of Bell inequalities and show a remarkable connection to CP
violation. We investigate the stability of entangled quantum systems pursuing
the question how possible decoherence might arise due to the interaction of the
system with its ``environment''. The decoherence is strikingly connected to the
entanglement loss of common entanglement measures. Finally, some outlook of the
field is presented.Comment: Lectures given at Quantum Coherence in Matter: from Quarks to Solids,
42. Internationale Universit\"atswochen f\"ur Theoretische Physik,
Schladming, Austria, Feb. 28 -- March 6, 2004, submitted to Lecture Notes in
Physics, Springer Verlag, 45 page
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